I've seen this before. I believe it is a die chip. The spot over the U is a die dot. Just something like a pot hole in that area. When it erodes out, then the area is raised on the coin. They always make nice die markers for varieties as they don't go away with continued use, they just get bigger. Did you note the bottom edge of the 6 in the date? It is a hub break. There are many examples from that year of that on different dies.